docs: def set_led(self, led, value):
          """Sets specified LED (value of 0 to 127) to the specified value, 0/False
          for off and 1 (or any True/non-zero value) for on.
          """
          if led < 0 or led > 127:
              raise ValueError('LED must be value of 0 to 127.')
          # Calculate position in byte buffer and bit offset of desired LED.
          pos = led // 8
          offset = led % 8
          if not value:
              # Turn off the specified LED (set bit to zero).
              self.buffer[pos] &= ~(1 << offset)
          else:
              # Turn on the speciried LED (set bit to one).
              self.buffer[pos] |= (1 << offset)